1. Field of the Invention
Aspects of the present invention relate to a method of controlling a color image forming apparatus, and more particularly to a method of controlling a color image forming apparatus to compensate for an output image distortion caused by mis-registration during the printing operation of a color document.
2. Description of the Related Art
Generally, an image forming apparatus converts an image file (such as a user's document created by an application program or an image captured by a user's digital camera) into encoded data, and prints the encoded data on a print medium (such as paper) so that the user can view the image. Examples of an image forming apparatus include a printer, a photocopier, a facsimile machine, a multi-functional product, etc.
An image forming apparatus capable of printing a color image includes a variety of toners (e.g., Cyan, Magenta, Yellow, and Black toners). Different colors of the print data are implemented by the combination of the above-mentioned toners having different colors, and are then printed on the print medium.
Unlike a black-and-white printer (also called a mono printer), the above-mentioned color image forming apparatus overwrites some colors on a single print medium several times in order to print a desired color image on the print medium. In this case, the color image forming apparatus has difficulty in correctly printing individual colors at desired positions due to a variety of factors resulting from printing a variety of colors on a single print medium. This problem is hereinafter referred to as a mis-registration.
Particularly, color distortion by which color dots disperse in all directions becomes serious at a boundary between composite black texts due to the mis-registration.
Generally, attributes of the print data are classified into an image, a graphic, and a text. Specifically, in the case of a composite black text, if the print data is determined to be a text, the image is printed in pure black. However, if the attributes of the print data are determined to be of an image, the black text is printed in composite colors. For example, if the color image forming apparatus based on four colors (i.e., C, M, Y, and K) determines the attributes of the print data to be of an image, the black text is printed in four colors (C, M, Y, and K). In this case, color dots having different colors may disperse in the vicinity of a text boundary due to the mis-registration, and the locations of the C, M, Y, and K dots on the screen are different from those of the printed dots. In other words, the C, M, Y, and K dots may be printed in the wrong locations due to mechanical errors resulting in the dispersion of the color dots. Accordingly, the desired image is distorted by the mis-registration, resulting in a deterioration of the printed image quality.